This disclosure relates to a suspension system for a multi-axle vehicle, and more particularly to providing a system, method, and control logic for implementing air suspension control for at least one axle on a trailer. More particularly, the disclosure is directed to a method that alters the axle air suspension pressure partially exhausting or removing air from air suspension bags to reduce tire wear when maneuvering at low speeds. The disclosure precludes a driver of the vehicle from reducing air pressure from the axle suspension above a predetermined speed, and thereby prevents overloaded conditions.
Federal regulation, namely Title 49 of the Code of Federal Regulations, Section 393.207, states that “the air suspension exhaust controls must not have the capability to exhaust air from the suspension system of one axle of a two-axle air suspension trailer unless the controls are either located on the trailer, or the power unit and trailer combination are not capable of traveling at a speed greater than ten miles per hour while the air is exhausted from the suspension system.”
One proposed solution is outlined in U.S. Pat. No. 5,052,713, the disclosure of which is incorporated herein by reference. The '713 patent is directed to a vehicle suspension system such as used in multi-axle tractor-trailers and other multi-axle vehicles. When maneuvering a trailer in a confined area such as a loading dock, torque is exerted on the trailer frame. One solution to the torque issue is to remove the load from all but one axle. The '713 patent teaches that air should be exhausted from the air bags on all but one axle in order to improve maneuverability at low speeds or during tight turns. Moreover, and per the federal regulation, the load must be redistributed to the multiple axles once the tight turn maneuvering is complete. Otherwise, the potential exists that a single axle may be overloaded, since the load has not been shifted to multiple axles. The overloading could result in potential damage to the trailer frame or dynamic loading encountered by the vehicle.
Although the '713 patent provides one solution, there are some downsides to this methodology and system. First, there is risk of damage to the air bags when all air is exhausted therefrom. The air bags may be pinched.
It is also important to note that the trailer will always be pivoting off the front axle, whether loaded or unloaded. It becomes important, therefore, that the system maintains the front axle with more pressure than the rear axle. That is, it is not just a question of unloading the rear axle, but assuring that the front axle has greater pressure than the rear axle.
There is also an issue of tire chattering that occurs when all of the pneumatic pressure is exhausted from one axle of the suspension system. Thus, there is a desire to prevent full exhaustion of the air suspension so that the tires associated with the axle are pushed to the ground.
Still another consideration relates to refilling the air bag. As will be appreciated, once maneuvering at low speeds is complete it becomes important to quickly re-distribute the load over the multiple axles. Known arrangements take as long as thirty (30) to forty (40) seconds to refill the exhausted air suspension. Unfortunately, in that time frame, the vehicle can be up to speed and the load has not been adequately re-distributed.
Yet another issue is that the air that supplies this system is obtained from the same reservoirs that are associated with the brake system.
There is also a potential advantage of using existing systems and components.
Thus, a need exists for an improved system that adds additional benefits in an economical, efficient manner.